The present invention relates to a method of sensing and processing images for a color video-endoscope, and to a video-endoscope implementing the method.
Patent FR-2 438 999 describes an endoscope for processing color information and for forming a read signal, in particular a signal compatible with a television set (a priori any television set of standardized format), i.e. for making color images of a field of observation (namely of objects situated in said field).
That French patent uses a lighting system based on the teaching of the U.S. Pat. No. 4,074,306 in which information about the image observed in the field scanned by the observation head of the endoscope is split into three primary colors, in particular Red, Green, and Blue (RGB). The original color image is then recreated by combining partial images in each of these three primary colors RGB. The three RGB images are formed by mechanically filtering the light used to illuminate the cavity being explored (by means of the observation head of the endoscope) by using a single light source associated with a rotary disk for providing RGB filtering of the light it provides. In a variant, the three RGB images may also be formed by splitting an image reflected from the field of observation by means of a series of dichroic mirrors.
French patent FR-2 438 999 thus differs from American U.S. Pat. No. 4,074,306 essentially in that the three separated light images, each containing data corresponding to an individual one of the primary colors RGB, are created by successively controlling a series of lamps that have short response times.
In addition, that French patent makes use of an individual light source for each of the primary colors (RGB) used in the video system adopted, which light is transmitted to the field of observation being explored by the head of the endoscope via a bundle of optical fibers. Furthermore, each of the primary color (RGB) images is formed in succession on a semiconductor image-forming device, and the output signals therefrom are coupled electrically to a memory for storing each of the read color signals individually, the color signals stored in the above memory being periodically applied to an image processing circuit for making the corresponding information available in a for-mat that is compatible with the format of a color receiver.
Nevertheless, the image of the observed field as reconstituted by analog means in this way does not have the brightness and contrast that is desirable in this kind of application, where it is essential to show up clearly the details of the field of observation that contain important optical information.
An object of the present invention is to eliminate the drawbacks of the prior art in such a manner as to obtain color images of the observed field having brightness and contrast that are better than those obtained in the prior art, with this having the additional advantage of an increase of at least 30% in the observation distance (between the read head of the video-endoscope and the field of observation).